![](https://i0.wp.com/www.raucci.net/wp-content/uploads/2021/09/dimostrazione-1024x744.png?resize=1024%2C744&ssl=1)
so, we can convince ourselves that:
\(\cos \left( {2x} \right) = {\cos ^2}\left( x \right) – {\sin ^2}\left( x \right)\)
\(\sin \left( {2x} \right) = 2\sin \left( x \right)\cos \left( x \right)\)
so, we can convince ourselves that:
\(\cos \left( {2x} \right) = {\cos ^2}\left( x \right) – {\sin ^2}\left( x \right)\)
\(\sin \left( {2x} \right) = 2\sin \left( x \right)\cos \left( x \right)\)
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